Combined biometrics capture system with ambient free infrared

ABSTRACT

An electronic device is disclosed herein that includes an infrared light source to emit infrared light, a rolling shutter sensor, and at least one processor. The at least one processor is to: cause the rolling shutter sensor to output a first signal corresponding to a first frame of image data during exposure to the infrared light, reset the rows of the rolling shutter sensor at a same time, cause the rolling shutter sensor to output a second signal corresponding to a second frame of image data without exposure to the infrared light from the infrared light source, determine a difference between the first signal and the second signal to generate an ambient infrared free frame, and recognize a face based on the ambient infrared free frame.

RELATED APPLICATION

This patent arises from a continuation of U.S. patent application Ser.No. 15/183,917, which was filed on Jun. 16, 2016. Priority is claimed toU.S. patent application Ser. No. 15/183,917. U.S. patent applicationSer. No. 15/183,917 is hereby incorporation by reference in itsentirety.

BACKGROUND

Electronic devices often include several cameras to collect infrared(IR) data according to various biometric systems. As used herein,biometric refers to metrics related to human characteristics. Thesemetrics may include, but are not limited to, facial features, patternsof the human iris, and eye gaze tracking. An electronic device mayinclude a facial recognition IR system, an iris recognition IR system,and an eye gaze tracking IR system. Each of these IR based systems mayhave separate and distinct hardware. Additionally, each IR system may belocated on the top side of the electronic device, where numerousantennas, sensors, other cameras, and speakers are located. Physicalspace at the front of the electronic device may be valuable and limited.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an electronic device that includes acombination camera system;

FIG. 2A is an illustration of a single camera system 200A thatimplements a plurality of technologies;

FIG. 2B is an illustration of a single camera system 200B thatimplements a plurality of technologies;

FIG. 3A is an illustration of a combined camera module with a liquidcrystal adjustable filter;

FIG. 3B is an illustration of a liquid crystal filter transmissionlevels graph and corresponding wavelength passbands;

FIG. 4A is an illustration of the implementation of an Fabry-Perotinterferometer;

FIG. 4B is an illustration of the incident angles of an FPI;

FIG. 4C is an illustration of an electrochromic filter/device withmultiple layers;

FIG. 4D is a graph that illustrates the wavelengths of light allowed topass with varying potentials applied an electrochromic filter/device;

FIG. 5A is an illustration of ambient free IR with a global shutter;

FIG. 5B is an illustration of the read out of a rolling shutter sensor;

FIG. 5C is an illustration of ambient free IR with a global shutter witha CMOS rolling shutter sensor;

FIG. 5D is an illustration of frame rates for various systems;

FIG. 6 is a process flow diagram of a method 600 for a combined camerasystem module; and

FIG. 7 is a block diagram showing a medium 700 that contains logic forenabling a combined IR capture system.

The same numbers are used throughout the disclosure and the figures toreference like components and features. Numbers in the 100 series referto features originally found in FIG. 1; numbers in the 200 series referto features originally found in FIG. 2; and so on.

DESCRIPTION

As discussed above, an electronic device may include several IR basedsystems with separate hardware. These systems are typically located onthe front of the device, near or at the top of the device when inportrait mode. Space along the top of the device is also used fornumerous antennas, indicators, cameras, speakers, and the like. Thus,the premium space at the front of the device may also be scarce.

Embodiments described herein relate generally to techniques for acombined biometrics capture system. A plurality of IR-based systems canbe combined, regardless of the IR passband used for varying IR-basedsystems. In embodiments, ambient free IR is implemented. As used herein,ambient free IR refers to an IR illuminated frame where the ambientilluminated frame is subtracted.

Some embodiments may be implemented in one or a combination of hardware,firmware, and software. Further, some embodiments may also beimplemented as instructions stored on a machine-readable medium, whichmay be read and executed by a computing platform to perform theoperations described herein. A machine-readable medium may include anymechanism for storing or transmitting information in a form readable bya machine, e.g., a computer. For example, a machine-readable medium mayinclude read only memory (ROM); random access memory (RAM); magneticdisk storage media; optical storage media; flash memory devices; orelectrical, optical, acoustical or other form of propagated signals,e.g., carrier waves, infrared signals, digital signals, or theinterfaces that transmit and/or receive signals, among others.

An embodiment is an implementation or example. Reference in thespecification to “an embodiment,” “one embodiment,” “some embodiments,”“various embodiments,” or “other embodiments” means that a particularfeature, structure, or characteristic described in connection with theembodiments is included in at least some embodiments, but notnecessarily all embodiments, of the present techniques. The variousappearances of “an embodiment,” “one embodiment,” or “some embodiments”are not necessarily all referring to the same embodiments. Elements oraspects from an embodiment can be combined with elements or aspects ofanother embodiment.

Not all components, features, structures, characteristics, etc.described and illustrated herein need be included in a particularembodiment or embodiments. If the specification states a component,feature, structure, or characteristic “may”, “might”, “can” or “could”be included, for example, that particular component, feature, structure,or characteristic is not required to be included. If the specificationor claim refers to “a” or “an” element, that does not mean there is onlyone of the element. If the specification or claims refer to “anadditional” element, that does not preclude there being more than one ofthe additional element.

It is to be noted that, although some embodiments have been described inreference to particular implementations, other implementations arepossible according to some embodiments. Additionally, the arrangementand/or order of circuit elements or other features illustrated in thedrawings and/or described herein need not be arranged in the particularway illustrated and described. Many other arrangements are possibleaccording to some embodiments.

In each system shown in a figure, the elements in some cases may eachhave a same reference number or a different reference number to suggestthat the elements represented could be different and/or similar.However, an element may be flexible enough to have differentimplementations and work with some or all of the systems shownn ordescribed herein. The various elements shown in the figures may be thesame or different. Which one is referred to as a first element and whichis called a second element is arbitrary.

FIG. 1 is a block diagram of an electronic device that includes acombination camera system. The electronic device 100 may be, forexample, a laptop computer, tablet computer, mobile phone, smart phone,or a wearable device, among others. The electronic device 100 mayinclude a central processing unit (CPU) 102 that is configured toexecute stored instructions, as well as a memory device 104 that storesinstructions that are executable by the CPU 102. The CPU may be coupledto the memory device 104 by a bus 106. Additionally, the CPU 102 can bea single core processor, a multi-core processor, a computing cluster, orany number of other configurations. Furthermore, the electronic device100 may include more than one CPU 102. The memory device 104 can includerandom access memory (RAM), read only memory (ROM), flash memory, or anyother suitable memory systems. For example, the memory device 104 mayinclude dynamic random access memory (DRAM).

The electronic device 100 also includes a graphics processing unit (GPU)108. As shown, the CPU 102 can be coupled through the bus 106 to the GPU108. The GPU 108 can be configured to perform any number of graphicsoperations within the electronic device 100. For example, the GPU 108can be configured to render or manipulate graphics images, graphicsframes, videos, or the like, to be displayed to a user of the electronicdevice 100. In some embodiments, the GPU 108 includes a number ofgraphics engines, wherein each graphics engine is configured to performspecific graphics tasks, or to execute specific types of workloads. Forexample, the GPU 108 may include an engine that processes infrared data.

The CPU 102 can be linked through the bus 106 to a display interface 110configured to connect the electronic device 100 to a display device 112.The display device 112 can include a display screen that is a built-incomponent of the electronic device 100. The display device 112 can alsoinclude a computer monitor, television, or projector, among others, thatis externally connected to the electronic device 100.

The CPU 102 can also be connected through the bus 106 to an input/output(I/O) device interface 114 configured to connect the electronic device100 to one or more I/O devices 116. The I/O devices 116 can include, forexample, a keyboard and a pointing device, wherein the pointing devicecan include a touchpad or a touchscreen, among others. The I/O devices116 can be built-in components of the electronic device 100, or can bedevices that are externally connected to the electronic device 100.

The electronic device 100 also includes a combined IR camera system 118for implementing several distinct recognition technologies. Byimplementing several different recognition technologies using a singlehardware system, the cost of the electronic device 100 may be reducedsince a single hardware system is used to replace three separatesystems. Additionally, the physical space within the electronic deviceused to implement the separate hardware systems may be reduced. Inembodiments, the combined IR camera system 118 captures variouspassbands of IR data, based on the particular biometric implementation.Moreover, the combined IR camera system 118 includes a rolling shuttersystem that can be used to implement a global shutter system. Theelimination of a global shutter system may also reduce costs associatedwith the electronic device 100. The use of a rolling shutter system toimplement a global shutter system also enables the use of a higherresolution sensor since global shutter sensors are typically onlycapable of capturing a minimum of 3 um pixels, whereas rolling shuttersensors pixels can typically capture a minimum of 0.9 um pixels. Thisdifferent in shutters of the combined IR camera system 118 can reducethe height of the optics hardware within the combined IR camera system118.

The electronic device may also include a storage device 124. The storagedevice 124 is a physical memory such as a hard drive, an optical drive,a flash drive, an array of drives, or any combinations thereof. Thestorage device 124 can store user data, such as audio files, videofiles, audio/video files, and picture files, among others. The storagedevice 124 can also store programming code such as device drivers,software applications, operating systems, and the like. The programmingcode stored to the storage device 124 may be executed by the CPU 102,GPU 108, or any other processors that may be included in the electronicdevice 100.

The CPU 102 may be linked through the bus 106 to cellular hardware 126.The cellular hardware 126 may be any cellular technology, for example,the 4G standard (International Mobile Telecommunications-Advanced(IMT-Advanced) Standard promulgated by the InternationalTelecommunications Union-Radio communication Sector (ITU-R)). In thismanner, the electronic device 100 may access any network 132 withoutbeing tethered or paired to another device, where the network 132 is acellular network.

The CPU 102 may also be linked through the bus 106 to WiFi hardware 128.The WiFi hardware is hardware according to WiFi standards (standardspromulgated as Institute of Electrical and Electronics Engineers' (IEEE)802.11 standards). The WiFi hardware 128 enables the electronic device100 to connect to the Internet using the Transmission Control Protocoland the Internet Protocol (TCP/IP), where the network 132 is theInternet. Accordingly, the electronic device 100 can enable end-to-endconnectivity with the Internet by addressing, routing, transmitting, andreceiving data according to the TCP/IP protocol without the use ofanother device. Additionally, a Bluetooth Interface 130 may be coupledto the CPU 102 through the bus 106. The Bluetooth Interface 130 is aninterface according to Bluetooth networks (based on the Bluetoothstandard promulgated by the Bluetooth Special Interest Group). TheBluetooth Interface 130 enables the electronic device 100 to be pairedwith other Bluetooth enabled devices through a personal area network(PAN). Accordingly, the network 132 may be a PAN. Examples of Bluetoothenabled devices include a laptop computer, desktop computer, ultrabook,tablet computer, mobile device, or server, among others.

The block diagram of FIG. 1 is not intended to indicate that theelectronic device 100 is to include all of the components shown inFIG. 1. Rather, the computing system 100 can include fewer or additionalcomponents not illustrated in FIG. 1 (e.g., sensors, power managementintegrated circuits, additional network interfaces, etc.). Theelectronic device 100 may include any number of additional componentsnot shown in FIG. 1, depending on the details of the specificimplementation. Furthermore, any of the functionalities of the CPU 102may be partially, or entirely, implemented in hardware and/or in aprocessor. For example, the functionality may be implemented with anapplication specific integrated circuit, in logic implemented in aprocessor, in logic implemented in a specialized graphics processingunit, or in any other device.

The combined IR camera system 118 described in FIG. 1 may be used toimplement a combined biometrics capture system. Biometric data is oftencaptured via emitting is invisible radiant energy and capturing theresultant scene. The IR image is created using invisible radiant energyand includes electromagnetic radiation with wavelengths longer thewavelengths of visible light. In embodiments, and IR wavelength canrange from the nominal red edge of the visible spectrum at 700nanometers (frequency 430 THz) to 1 mm (300 GHz).

The IR passband of each biometric system may differ. For biometric datacapture, the passband must be as narrow as possible for its intendeduse. If the passband is made too wide, ambient sun originated IR willaffect the sensitivity of the IR capture, which can lead to spoofing.Spoofing occurs when a person or program successfully masquerades asanother by falsifying data. Additionally, a passband that is too wideaffects the ability to provide a consistent image via IR in diverselightning or weather conditions, and allows for subtle changes inappearance including facial hair, cosmetic make up, eye wear, etc. Anaccurate passband also enables support of IR capture in darkness so thatusers are not frustrated and abandoning the system.

For example, a biometric system that track the eye gaze of a usertypically uses a passband that is greater than 880 nanometers (nm),which is invisible for humans. An iris scanning system typicallyimplements a passband that includes 800 nm, which may be visible to somehumans. When these two systems are combined, any visible IR light bandcould be annoying to the user. In other words, during eye gaze tracking,a visible passband at 800 nm may be perceived by a user. In embodiments,eye gazing tracking is continuous and thus a passband of 880 nm orgreater is better to use in an eye gaze tracking system because it isinvisible to a user.

An iris scan system and an IR-based facial recognition system are bothbiometric logging systems that can exist in same system according tovarious operating system requirements. An iris scan system and anIR-based facial recognition system also both have different applicationareas. For example, an iris scanning system is much more secure andwould be used with applications that require a high level of security,such as banking login applications. Facial recognition can be used forapplications where a heightened level of security is not required.Moreover, eye gazing is a user interface input system that also is basedon IR light and detection of retina and pupil movements. It would beadvantageous if all of the cameras could be merged in to one.

Table 1 details the differences in several requirements for each of aface recognition, iris scan, and eye gaze IR-based system. FaceRecognition Iris Scan Eye Gaze Resolu- VGA 2 megapixels >4 megapixelstion FOV >60 HFOV 30 DFOV >60 HFOV IR 840-870 nm 800-850 nm >880 nmPass- band Sensor Global Rolling Rolling Type Shutter Shutter ShutterFocal NA 4 mm NA Length

The requirements described above are exemplary, and can vary acrosssystems. Additionally, face recognition also requires ambient free IR.In ambient free IR, the ambient IR level is determined, and the ambientIR level is subtracted from the captured IR frames. The ambient IR levelis used as a reference so that the resulting IR image capture does notchange based on ambient lighting conditions. In embodiments, facerecognition and the associated ambient IR requires a global shuttersensor. A global shutter sensor is implemented utilizing a rollingshutter according to the present techniques. Additionally, thetechniques described herein enable a low cost CMOS sensor and muchhigher resolutions to be captured in a global shutter format.

Further, a camera hardware system is presented that covers all IR-basedsystems. For ease of description, the three IR-based systems describedherein are face recognition, iris scan, and eye gaze. However, anyIR-based biometric system may be combined into a single module accordingto the present techniques. In embodiments, a plurality of IR-basedsystems are combined via an adjustable IR pass filter, where thepassband is adjusted by an electrical means to realize the desiredpassband of the system to be implemented. Moreover, the presenttechniques implement the ambient free IR using an adjustable filter anda rolling shutter sensor instead of global shutter sensor.

FIG. 2A is an illustration of a single camera system 200A thatimplements a plurality of IR-based systems. As discussed above, thecombined capture system according to the present techniques can be usedto implement each of a face recognition, iris scan, and eye gaze system.In this manner, the hardware used to realize each of the three systemsis reduced.

The camera system 200A includes a printed circuit board (PCB) 202. ThePCB 202 may be used to electrically connect the camera system 200 toother components that may be included in an electrical device. In somecases, the PCB 202 is a main circuit board or motherboard of the device200. An image sensor 204 may be coupled with the PCB 200. The imagesensor 204 may be any device that converts an optical image into anelectrical signal. For example, the image sensor 204 may be a chargecoupled device (CCD) sensor or a complementary metal-oxide-semiconductor(CMOS) sensor. A processor may be configured to read an electricalsignal from the image sensor 204 and control an IR pass filter 206 toobtain the correct passband for the particular application or use of thecamera system 200. The IR pass filter 206 is an optional component of acombined camera system according to the present techniques. The IR passfilter 206 may be used to reduce any out of spectrum signal that ispassed to the IR pass filter 206. The IR pass filter 206 may alsofunction as a dust shield and protect the underlying electricalcomponents.

A lens system 208 may be any optical device that is to focus light ontothe image sensor 204 through the IR pass filter 206. In embodiments, thelens system 208 may be a compound lens or an array of lenses. Aprocessor may be configured to control the focal length of the lenssystem 208. A liquid crystal (LC) or electrochromatic filter 210 isplaced on top of the camera system 200. A liquid crystal filter isdescribed more fully with respect to FIG. 3A. An electrochromatic filteris described more fully with respect to FIG. 4C.

The filter 210 may be encompassed in glass that is used to cover a localopening 212 of the camera system 200. As illustrated, the camera system200A has a local opening 212 of width D1. The glass may function as dustshield, and is preferably an IR pass instead of plain all pass glass. Inembodiments, the glass may provide an additional IR pass filter. Inembodiments, electrical control of the LC/electrochromatic filter 210enables the system to vary to wavelengths that are allowed to pass.

In some cases, the stop band provided by the LC/electrochromatic filter210 may be soft. Put another way, the LC/electrochromatic filter 210 mayallow wavelengths outside of the desired wavelengths to pass. The IRfilter 206, and any additional IR filter provides a sharp cutoff bandthat can be used to refine the stop bands. In embodiments, by usingglass that includes an infrared cut off (IRCF), the camera system 200Ais provided with provide sharp edges at least for the outer edges ofcombined IR passbands of a plurality of IR-based systems. If thetolerances of all components, including IR sources, are narrowed,additional stop bands can be built and active IR filter requirements foredge steepness is reduced.

For example, the LC/electrochromatic adjustable filter 210 may allowtransmission of undesired wavelengths, and the optional IR pass filter206 can be used to filter the undesirable signals and prevent them frompassing as discussed above. The IR pass filter can also serve as a dustshield. Moreover, the desired wavelengths may be on the edge of therange of the adjustable range filter (such as the LC/electrochromaticfilter) such that the transmitted wavelengths response becomesinaccurate. The IR pass filter can provide more a precise definition forsystem spectrum limits. In embodiments, the IR pass filter 206 can bereplaced by glass that provides dust seal without a spectrum filtereffect.

The passbands 214 illustrate the wavelengths allowed to pass viaelectrical control of the LC/electrochromatic filter 210 combined withan IR pass filter 206. As illustrated, the passband 216 of the irisrecognition system may begin at 800 nm with an optional stop band 222between the iris recognition system and the face recognition systempassband 218. The eye gaze system passband 220 occurs at approximately880 nm.

The stopband 222 between the iris recognition system passband 216 andthe face recognition system passband 218 is optional. In embodiments,due to manufacturing variations, which include the center frequency andwidth of the emitted spectrum band, the thermal variation of the IRlight source, and other similar variations, tunable filter the passbandssuch as the passband from the LC/electrochromatic filter 210 may not benarrow. However, some tolerance can be introduced to the system and thepassband can be made wider due to variations. If these variations aresmall enough and desired passband of each of a plurality of systems arewide enough apart, an optional stopband between each system passband canbe used to define sharp stopbands for each system.

FIG. 3A is an illustration of a combined camera module with liquidcrystal adjustable filter 302. As illustrated, the LC adjustable filter302 includes a liquid crystal layer. In embodiments, the liquid crystallayer may be about 5 um thick. The liquid crystal layer may include LClayer 1 304, LC layer 2 306, LC layer 3 308. Each layer of layers 304,306, and 308 may be made reflective for certain wavelengths by selectinga combination of an excitation frequency, voltage, and LC material. Inembodiments, crystal alignment and thickness will also affect thebandwidth of reflectance of the LC material. If the frequency ischanged, the material changes to scattering or if the excitation isdisabled the LC can become fully transmissive for all bandwidths. Thus,by selecting particular parameters, including an excitation voltage andfrequency, the LC adjustable filter 302 may be reflective, transmissive,partially reflective, or partially transmissive. The light then passesthrough the lens 310 to an image sensor 312.

FIG. 3B is an illustration of a liquid crystal filter transmissionlevels graph 320 and corresponding wavelength passbands 322. Anexcitation frequency and voltage may be applied to one or more layers ofthe LC/electrochromatic adjustable filter 302 to transmit infrared lightas illustrated at the transmission levels graph 320. For example, thetransmission levels graph 320 includes an x-axis 326 that represents thewavelength of light in nanometers (nm). A y-axis 324 represents atransmission percentage of infrared light.

When varying levels of voltage are applied to an LC/electrochromaticadjustable filter, all infrared light may be enabled to pass, asillustrated at reference number 328. At reference number 330, thetransmission/reflectance level of wavelengths of an iris scan system isrepresented. At reference number 332, the transmission/reflectance levelof wavelengths of a face recognition system is represented.Additionally, at reference number 334, the transmission/reflectancelevel of wavelengths of an eye gaze system is represented.

Based on the transmission/reflectance on the graph 320, variouswavelengths are passed as illustrated by the passbands 322. The irisscan passband 336 begins at 800 nm. The face recognition passband 338occurs around 860 nm. Additionally, the eye gaze passband 340 occursaround 880 nm. In embodiments, the iris scan passband is not madereflective. The result is a sharp transmission at the band defined bythe IR band pass filter and passing IR scan LC sub-band as illustratedat reference number 324. In particular, the transmission at referencenumber 324 is a result of sharp cut off IR pass. It has smallreflectance at the iris scan passband 336 since that layer has anon-ideal response. The iris scan passband response falls off accordingto response of the face recognition passband 338 reflectance.Accordingly, there are two small dips at reference number 336 where theface recognition passband reflectance starts to decline but the IR passfilter rejection band increases. The next dip is where the eye gazepassband 340 has small transmission as its reflectance may not be notideal.

Accordingly, an LC film can be excited by a frequency that makes itreflective or scattering by another frequency. Without excitation, theLC film is fully transmissive. In embodiments, the reflectance of the LCis 50%, as it works for one polarization. One can add another for otherpolarization of light and make it 100% reflective. Bands for reflectanceas narrow as 10 nm are possible by selecting polarizations parameters ofvarious LC layers, such as the orientation of each layer with respect tothe other layers. In order to filter both polarizations, two layers maybe in a 90 ninety-degree perpendicular orientation to each other. Asillustrated in FIG. 3A, there may be two separate LC systems or portionsof LC material sandwiched between glasses that have their moleculesaligned in perpendicular planes, i.e., each operating with onepolarization component of light.

In some examples, a liquid crystal layer can be made reflective forcertain wavelengths by selecting the excitation frequency, voltage, andLC material. For example, the LC layer can be 5 micrometers thick. Insome examples, crystal alignment and thickness can also affect abandwidth of reflectance. For example, differing reflectance can beachieved using different crystal alignments and layer thickness. In someexamples, if a frequency is changed the material changes to scattering.In some examples, if excitation is disabled, the liquid crystal layercan be fully transmissive for all bandwidths. In some examples, agreatest reflectance for one liquid crystal layer can be 50% as thelayer works through polarization. In some examples, a second liquidcrystal layer can be added for another polarization of light and makethe greatest reflectance for the two layers up to 100% reflective. Insome examples, for narrow bands for reflectance, 10 micrometer thickliquid crystal layers can be used.

Referring now to FIG. 2B, a single camera system 200B that implements aplurality of technologies is illustrated. Similar to FIG. 2A, the camerasystem 200B includes a PCB 202, an image sensor 204, and IR pass filter208, and a lens system 208. However, the local opening 228 of the camerasystem 200B may be implemented using a Fabry-Perot interferometer (FPI)226.

An optical system typically has many openings, or structures that limitthe ray bundles, where ray bundles are also known as pencils of light.These structures may be the edge of a lens, or a ring (sheet that limitslight through circular ring), or other fixture that holds an opticalelement in place. In some cases, a special element such as a diaphragmmay be placed in the optical path to limit the light admitted by thesystem.

Generally, these structures are called stops, and the aperture stop isthe stop that primarily determines the ray cone angle and brightness atthe image point. Sometimes stops and diaphragms are referred to asapertures, even when they are not the aperture stop of the system.Accordingly, there could be smaller aperture that defines the limits oflight that reaches a sensor. While the opening 228 may define anaperture of the camera system 200B, the opening 228 is not necessarilythe aperture stop of the system 200B.

The FPI 226 can have a passband as narrow as 10-15 nm with accuracy of+−1 nm for the center peak of passband. The passband of the FPI 226 maybe referred to as full width half maximum (FWHM). The switching speed ofthe FPI 226 is below 10 ms or faster. The speed of switching betweenpassbands varies depending design approach. FP's however require thatincident angles are within +/−5 degrees. Aperture at range of 1-4 mmexists today. The present techniques include additional optics in case alarger than +/−5 FOV is required, which may be the case in someembodiments.

FIG. 4A is an illustration of the implementation of a Fabry-Perotinterferometer 400A. The FPI 400A may include an actuator 412 that is toadjust the size of a tunable air gap 402. In embodiments, the actuator412 may be a MEMS electrostatic actuator or a piezo-electric crystalactuator. The actuator 412 may be used to control a spectrum of lightpassing through the FPI 400A by changing the distance between a pair ofmirrors 404 and 406. This can be done by either moving both or at leastone of the mirrors 404 and 406. As the distance 402 between mirrors 404and 406 changes, the passband will shift as a function of excitation ofthe actuator. Excitation of the actuator will cause the mirrors 404 and406 of the FPI 400 to move relative to each other. The incident angle ischanged as a result of this movement, resulting in a passband shift.Accordingly, incoming light 408 may be broadband or white light. Afterpassing through the FPI 400A, the transmitted light 410 has a narrowwavelength band.

In embodiments, the FPI 400A consists of two mirrors separated by adistance. In its simplest form, the FPI may be a slab or an etalon whereincident light is reflected back and forth between the etalon faces,thus forming constructive and destructive standing wave conditions for acertain wavelength. In effect, the FPI 400A transmits certain narrowwavelength bands while blocks the others. A tunable filter can beconstructed by placing two mirrors close to each other while adjustingthe gap between them. That is where the parallelism of the optical gapand the precision of gap adjustment become critical. The spectralresolution of the FPI 400A depends on the reflectivity of the mirrorsand the gap between the mirrors while the passed wavelengths depend onlyon the gap. In the FPI 400A, the resolution and the Free Spectral Range,i.e. the distance between two multiple order passbands, are inverselyrelated—having a very high resolution results in a very small workingrange and vice versa.

In embodiments the FPI 400A can have passband as narrow as 10-15 nm withaccuracy of +/−1 nm. In embodiments, the passband may also be referredto as a full width half maximum (FWHM) band. The switching speed of theFPI 400A is below 10 ms or faster. As used herein, the switching speedrefers to the speed at which the passband is changed. The speed variesdepending design approach of the FPI. FP's however require that incidentangles are within +−5 degrees.

As noted above, the actuator 412 may be a MEMS electrostatic actuator ora piezo-electric crystal actuator. In embodiments, the MEMS based FPImay be a mass-producible optical MEMS (MOEMS) based based FPI asdescribed in “Tunable MOEMS Fabry-Perot Interferometer for MiniaturizedSpectral Sensing in Near-Infrared” by Rissanen et al., VTT TechnicalResearch Centre of Finland, Tietotie 3, Espoo, Finland in Proc. of SPIE2014. Thus two different manufacturing platforms exist for FPIs: opticalMEMS-based chips (MOEMS FPI or MEMS FPI) and the separately assembledpiezo-actuated tunable filter modules (Piezo FPI or PFPI). These twoplatforms enable sensing solutions for both high-volume MOEMSapplications as well as customized high performance PFPI opticalinstruments.

In PFPI modules found in broadband hyperspectral imagers, large opticalapertures up to 15 mm in size can be realized due to the robust, thickmirror substrates on which the thin-film reflectors are deposited andthen assembled together using commercial piezo actuators. MEMS FP's aretunable optical filters, which enable miniaturization of spectralimagers into small, mass producible hand-held sensors with versatileoptical measurement capabilities. These MEMS based FP's are also veryrobust with regard to mechanical shock. Until now, these manyapplication demonstrations have been mostly realized with piezo-actuatedFP's fabricated by non-monolithical assembly method, suitable forachieving very large optical apertures and with capacity tosmall-to-medium volumes. However large-volume production of MEMSmanufacturing supports the potential for emerging applications also inlarge-volume applications, such as in consumer/mobile products.

Accordingly, two techniques can be used to realize an FPI according tothe present techniques. First, a MEMS base FPI, where mirrors areactuated by an electrostatic actuator and second, a PFPI where mirrordistance is actuated by piezo actuator. With the PFPI, the manufacturingprocess is a non-monolithical assembly method, contrary to fullmonolithic process of MEMS. As used herein, monolithic refers to thewhole structure being processed in semiconductor process on a wafer.

In embodiments, MEMS Fabry-Perot interferometers (FPIs) are tunableoptical filters, which enable miniaturization of spectrometers into massproducible hand-held sensors with versatile measurement capabilities.The Fabry-Perot interferometer consists of two reflective mirrorsurfaces, typically thin film Bragg reflectors, with a gap between themirrors and integrated electrodes within the membrane structure. Thepassband wavelength of the filter is tuned by adjusting the distancebetween the mirrors.

An aperture at range of 1-4 mm exists today. There also other sourcesand these systems will emerge in coming years. Thus on top of FPI oneneeds to place additional optics in case larger than +/−5 FOV isrequired (as it is in this case). If alpha angle is too large thetransmission goes zero. The alpha angle is the incident angle. Thechallenge of increasing size of the optical aperture of a MEMS structurearises from the extremely high aspect ratios. Increasing the size ofoptical aperture up to 4 mm with the tuning electrodes surrounding theaperture means the entire released membrane needs to be more than 5 mm.The typical air gap of visible wavelength FP's is of the order of 1.6μm, thus resulting in a several mm-diameter membranes separated withμm-range gap.

FIG. 4B is an illustration of the incident angles of an FPI. In FIG. 4B,and incident angle a 402 is illustrated. R1 452 is a first reflectedwavelength, R2 454 is a second reflected wavelength, T1 is a firsttransmitted wavelength, and T2 is a second transmitted wavelength.Additionally, M1 460 is a first mirror and M2 462 is a second mirror,where the mirror M1 460 and the mirror M2 462 are separated by adistance d 464.

FIG. 4C is an illustration of an electrochromic filter/device 400C withmultiple layers. The electrochromic filter/device 400C includes atransparent electrode 470A, a transparent electrode 470B, a firstelectrochromic layer 472A, a second electrochromic layer 472B, and anelectrolyte layer 474. A voltage 476 may be applied to each transparentelectrode 470A and transparent electrode 470B, thereby controlling thewavelengths of light 478 that are allowed to pass. In embodiments, threepieces of glass—one for first NIR band, another for second infraredband, and so on may be cemented together. Typical electrochromicstructures use an electrochromic liquid, polymer or gel such as theelectrolyte 474 captured between two layers of transparent substrate,such as glass or plastic as represented by transparent electrodes 470Aand 470B. Electrodes allow a potential to be applied to the liquid,polymer or gel to achieve the desired effect. Electrochromic materialwill absorb the certain wavelengths when activated.

FIG. 4D is a graph 400D that illustrates the wavelengths of lightallowed to pass with varying potentials applied to an electrochromicfilter/device. The x-axis 480 of the graph 400D represents thewavelength allowed to pass, while the y-axis 482 represents thepotential applied to an electrolyte layer. By applying differentpotentials to the electrolyte layer, various levels of transmission onabsorbance can be obtained as illustrated by line 484 and line 486.

The present techniques describe the combination of separate biometricrecognition applications into a single hardware unit. Recognitionapplications such as face recognition can require ambient free IR asdiscussed above. Their algorithm which is standard API is expecting sucha format, and thus it would be advantageous to have ambient free IR witha CMOS rolling shutter sensor as well. This can be done so that oneglobal shutter frame is taken without IR light. This helps to remove theambient IR levels from signal. A benefit of the global shutter sensor isthat timing of IR flash is very accurate and there are no limitations onin timings of rolling shutter, like exposure time and number of rows andinterface speed i.e. readout-time, within specified frame rate.

The present techniques enable the use of a rolling shutter sensor but inglobal reset mode. This means that all rows of the rolling shutter arereset in same time, and exposed for some same time. After desiredexposure time the controller gives command for tunable IR pass filter tochange its passband. This happens in short time e.g. in 1 ms. Pixels canbe read in any time as they are not any more exposed to IR. All framesare started with a global reset. After exposure time, the IR filterpassband is changed on the rejection band of IR PASS filter which is outof application bands of the face scan application.

FIG. 5A is an illustration of ambient free IR with a global shutter.Reference number 502 illustrates the capture of a frame one, andreference number 504 illustrates the capture of a frame two. An x-axis506A and 506B represents time for each frame. A y-axis 508A and 508Brepresents a line number for each frame.

As illustrated, in frame 1 502, a command reset 510A occurs to reseteach line of the rolling shutter. During the integration timerepresented by the dashed lines, the flash could occur at any time.Thus, the IR light pulse could occur at any time 512A after the commonreset 510A. While the IR pulse can be at any time, it does not need tobe any longer than the actual integration time. In embodiments, the IRpulse is the same as the actual integration time as all IR outside of IRflash pulse is considered noise. The integration time, as describedherein, it the time between a common reset and the common sample andhold.

A common sample and hold occurs at reference number 514A. At thismoment, the change on all pixels is moved to a storage capacitor whichkeeps the change signal stabile during readout of all pixels. After thecommon sample and hold, a burst readout time occurs as indicated by thesolid lines 516A. Similarly, in frame 2 504, the ambient IR frame iscaptured. A command reset 510B occurs to reset each line of the rollingshutter. During the integration time represented by the dashed lines,ambient IR is integrated. A common sample and hold occurs at referencenumber 514B. After the common sample and hold, a burst readout timeoccurs as indicated by the solid lines 516B. Ambient IR is thus sensedand this image can be later derived from the first frame that is sum ofambient and IR flash illumination. Put another way, the second may besubtracted from the first frame to obtain ambient free IR. Accordingly,the rolling shutter sensor may be a sensor that implements a shuttersuch that an image or frame of video is captured by scanning across thescene rapidly, either vertically or horizontally. With a global shuttersensor, every pixel of an image or frame of video is exposedsimultaneously at the same instant in time. The line 518 illustrates aperiod of time 518A where the IR pulse occurs in the first frame 502 inorder to capture the ambient free IR. At line 518, a capture occurs withhelp or IR pulse/flash with both IR flash and ambient IR present. Atframe 504, only the ambient IR light is present and no additional IRflash light is present. The frame 504 is then subtracted from the frame502 to obtain an ambient IR free image.

In FIG. 5A, all pixels are exposed at same time. No motion artifactsoccur, and the same ambient condition exists for each pixel. Moreover,there is a high frame rate with accurate ambient and IR. Additionally,the IR light source duration is short which results in a lower number ofthermal issues and lower power consumption due to accurate conditions ofthe coordinated ambient and IR integration time. The ambient IR captureand the IR integration time can also be different as long as ratio isknown and taken account in ambient subtraction operation.

FIG. 5B is an illustration 50013 of the read out of a rolling shuttersensor. As discussed above, the rolling shutter sensor differs from theglobal shutter sensor in that it does not have storage capacitor. Thusthe signal needs to be read right after desired integration time. Atreference number 522, a plurality of lines 532 are illustrated thatrepresent the pixels of an image along a time line 530. As illustrated,each line is read right after its integration time ends, and then theline is reset. In embodiments, all lines are not reset simultaneously,as the limited readout speed would lead to unequal integration time ofeach line as signal would continue to be integrated because it is notmoved to storage capacitor. The lines are also reset at different times,which can be called rolling reset. The rolling resets are illustrated assquares along each line 532, with the transfer to a storage capacitorrepresented by a circle along the lines 532. In order for all have thesame integration of IR pulse, the pulse should be starting from themoment of first line start until end of the last line. This time islonger than integration time of each row because it also comprises thereadout time of whole frame limited by reading speed and conversionspeed of signal in sensor to digital and interface limitations.

The IR pulse thus needs to be on a longer time than in a global resetsensor. Additionally, the next frame's first line integration typicallystarts already the last line of previous frame has been exposed. Thismeans that next frame may be corrupted as part of the lines in imagewill be illuminated by the IR pulse and part of that with ambient only.This frame is bad and needs to be discarded. Thus, the IR pulse sequence520 shows various illumination on 528A, 528B, and 528C where the IRpulse occurs. The frame 524 is a useable frame, however the frame 526should be discarded. A third frame could be the ambient (no IR flash)frame, but again a fourth frame has already started before last lineexposed fully from third frame and fourth frame would be to be discardedas that is partly ambient-only exposed so flash cannot be fired for it.A fifth frame in this sequence would again be an IR flash pulsed frame.

FIG. 5C is an illustration 500C of ambient free IR with a global shutterwith a CMOS rolling shutter sensor. FIG. 5C is similar to FIG. 5A.However, the change filter 536A and 536B enables a CMOS rolling shuttersensor to be used. The CMOS rolling shutter implementation has a globalreset feature and it is usable as pixels are non-exposed by light as theadjustable filter is used as “global shutter.” Put another way, theadjustable filter is changed to realize the global shutter. When theillumination and integration time have elapsed, the filter passband isset outside of desired band and no signal is received. All lines can bethus read without getting unwanted excess integration of light.

FIG. 5D is an illustration of frame rates for various systems. The imagecollection system 540 represents a system with a frame rate with aglobal shutter sensor. The image collection system 542 represents asystem with a rolling shutter, and the image collection system 544represents a system with a rolling shutter with global reset and tunablefilter as described in FIG. 5C. The frame rate of the image collectionsystem 540 is the same as the frame rate of the image collection system544. However, the frame rate of the image collection system 542 leads tolower frame rate and there is unusable wait time due to two discardedframes. The two system are approximately equal when the filter can beset to on-off in relative short time compared to the readout time andback to on desired band for next frame that is much shorter than frametime. The duration to move the passband back on to the face IR passbandwould directly add to overall time used for one frame.

FIG. 6 is a process flow diagram of a method 600 for a combined camerasystem module. At block 602, the camera system to be implemented isdetermined. In examples, the system to be implemented may be one of aface recognition, iris scan, or eye gaze system.

At block 604, the control voltage and/or frequency of the LC filter,FPI, or electrochromatic filter is adjusted to obtain the IR passbandwidth and center frequency that corresponds to the system selected atblock 602. As used herein, the center frequency is the center frequencyof the passband of a tunable filter. At block 606, it is determined ifthe camera system to be implemented is face recognition. If facerecognition is to be implemented, process flow continues to block 608.

At block 608 an IR LED is started. In embodiments, the IR LED is a NIRLED with a wavelength spectrum at approximately 700-1200 nm. At block610, the global reset is adjusted. As discussed above, the global resetmay be adjusted using a rolling camera shutter system. At block 612,after the exposure, the passband of the tunable filter is changed to bethe stop band of an IR pass filter. Alternatively, the tunable filtermay be adjusted such that there is a low sensitivity in case an IR passfilter is not present.

At block 614, the LED is stopped. At block 615, the frequency is changedback to the IR passband. At block 616, the global reset is adjusted. Atblock 618, after the exposure, change the IR passband out of the IRCFfrequency. In embodiments, the global reset is adjusted a second time toobtain an image. Specifically, a first frame with IR illumination iscaptured, and a first reset is applied. A second frame is capturedwithout IR light where only ambient IR light is present. Thenunilluminated second frame is subtracted from the illuminated firstframe and an ambient free IR frame is obtained. In this manner, a cleanand consistent image is obtained, regardless of the ambient lightning,weather, or even complete darkness. This ambient IR technique results ina better tolerance for changes in the face, such as facial hair andcosmetic makeup, with no need for multiple enrollments resulting in abetter user experience.

This process flow diagram is not intended to indicate that the blocks ofthe example process 600 are to be executed in any particular order, orthat all of the blocks are to be included in every case. Further, anynumber of additional blocks not shown may be included within the exampleprocess 700, depending on the details of the specific implementation.

FIG. 7 is a block diagram showing a medium 700 that contains logic forenabling a combined IR capture system. The medium 700 may be acomputer-readable medium, including a non-transitory medium that storescode that can be accessed by a processor 702 over a computer bus 704.For example, the computer-readable medium 700 can be volatile ornon-volatile data storage device. The medium 700 can also be a logicunit, such as an Application Specific Integrated Circuit (ASIC), a FieldProgrammable Gate Array (FPGA), or an arrangement of logic gatesimplemented in one or more integrated circuits, for example.

The medium 700 may include modules 706-710 configured to perform thetechniques described herein. For example, a tunable module 706 may beconfigured to determine a passband that corresponds to a biometriccapture application. The tunable module 706 may also adjust a voltageand frequency of an adjustable filter in response to the captureapplication and associated passband. A shutter module 708 may beconfigured to implement a global shutter system via a rolling shuttersystem in response to a face recognition capture application. A capturemodule 710 may be configured to capture IR images. In some embodiments,the modules 706-710 may be modules of computer code configured to directthe operations of the processor 702.

The block diagram of FIG. 7 is not intended to indicate that the medium700 is to include all of the components shown in FIG. 7. Further, themedium 700 may include any number of additional components not shown inFIG. 7, depending on the details of the specific implementation.

Example 1 is an apparatus for a combined camera system. The apparatusincludes an adjustable pass filter, wherein a passband of the filter iselectrically adjusted; and a rolling shutter sensor, wherein anadjustable filter is to implement a global shutter and a rolling shuttersensor global reset.

Example 2 includes the apparatus of example 1, including or excludingoptional features. In this example, the adjustable pass filter is atunable IR pass filter.

Example 3 includes the apparatus of any one of examples 1 to 2,including or excluding optional features. In this example, theadjustable pass filter is a liquid crystal filter. Optionally, theliquid crystal filter comprises a plurality of liquid crystal layers,wherein each layer is to reflect or transmit certain passbands.

Example 4 includes the apparatus of any one of examples 1 to 3,including or excluding optional features. In this example, theadjustable pass filter is an electrochromatic filter.

Example 5 includes the apparatus of any one of examples 1 to 4,including or excluding optional features. In this example, theadjustable pass filter is a Fabry-Perot interferometer (FPI).Optionally, the Fabry-Perot interferometer (FPI) changes the passband asa function of excitation of an actuator. Optionally, the Fabry-Perotinterferometer (FPI) is a micro-electro-mechanical (MEMS) Fabry-Perotinterferometer (FPI). Optionally, the Fabry-Perot interferometer (FPI)is a piezo-actuated Fabry-Perot interferometer (FPI).

Example 6 includes the apparatus of any one of examples 1 to 5,including or excluding optional features. In this example, the apparatusincludes an IR filter, wherein the IR filter is to provide a sharpcutoff band to refine the adjustable passband of the adjustable passfilter.

Example 7 includes the apparatus of any one of examples 1 to 6,including or excluding optional features. In this example, theadjustable pass filter is adjusted for a passband that corresponds to abiometric recognition application.

Example 8 includes the apparatus of any one of examples 1 to 7,including or excluding optional features. In this example, theadjustable IR pass filter is adjusted for a passband that corresponds toa face recognition, iris scan, or eye gaze application on the fly.

Example 9 is a method for implementing a combined IR capture system. Themethod includes determining a passband that corresponds to a biometriccapture application; adjusting a voltage and frequency of an adjustablepass filter in response to the capture application and associatedpassband; and in response to a face recognition capture application,implementing a global shutter system and a rolling shutter sensor globalreset.

Example 10 includes the method of example 9, including or excludingoptional features. In this example, the biometric capture application isone of a face recognition, iris scan, or eye gaze application.

Example 11 includes the method of any one of examples 9 to 10, includingor excluding optional features. In this example, a second filter is torefine the passband via a plurality of stopbands.

Example 12 includes the method of any one of examples 9 to 11, includingor excluding optional features. In this example, the adjustable passfilter is a liquid crystal filter. Optionally, the liquid crystal filtercomprises a plurality of liquid crystal layers, wherein each layer is toreflect or transmit particular passbands.

Example 13 includes the method of any one of examples 9 to 12, includingor excluding optional features. In this example, the adjustable passfilter is an electrochromatic filter.

Example 14 includes the method of any one of examples 9 to 13, includingor excluding optional features. In this example, the adjustable passfilter is a Fabry-Perot interferometer (FPI). Optionally, theFabry-Perot interferometer (FPI) changes the passband as a function ofexcitation of an actuator.

Example 15 includes the method of any one of examples 9 to 14, includingor excluding optional features. In this example, the adjustable passfilter is a micro-electro-mechanical (MEMS) Fabry-Perot interferometer(FPI).

Example 16 includes the method of any one of examples 9 to 15, includingor excluding optional features. In this example, the adjustable passfilter is a piezo-actuated Fabry-Perot interferometer (FPI).

Example 17 includes the method of any one of examples 9 to 16, includingor excluding optional features. In this example, the global reset isapplied to the rolling shutter system after each face recognitioncapture.

Example 18 is a system for a combined IR capture system. The systemincludes a display; a camera; a memory that is to store instructions andthat is communicatively coupled to the camera and the display; and aprocessor communicatively coupled to the camera, the display, and thememory, wherein when the processor is to execute the instructions, theprocessor is to: determine a passband that corresponds to a biometriccapture application; adjust a voltage and frequency of an adjustablepass filter in response to the capture application and associatedpassband; and in response to a face recognition capture application,implement a global shutter system and a rolling shutter sensor globalreset.

Example 19 includes the system of example 18, including or excludingoptional features. In this example, the biometric capture application isone of a face recognition, iris scan, or eye gaze application.

Example 20 includes the system of any one of examples 18 to 19,including or excluding optional features. In this example, a secondfilter is to refine the passband via a plurality of stopbands.

Example 21 includes the system of any one of examples 18 to 20,including or excluding optional features. In this example, theadjustable pass filter is a liquid crystal filter. Optionally, theliquid crystal filter comprises a plurality of liquid crystal layers,wherein each layer is to reflect or transmit particular passbands.

Example 22 includes the system of any one of examples 18 to 21,including or excluding optional features. In this example, theadjustable pass filter is an electrochromatic filter.

Example 23 includes the system of any one of examples 18 to 22,including or excluding optional features. In this example, theadjustable pass filter is a Fabry-Perot interferometer (FPI).Optionally, the Fabry-Perot interferometer (FPI) changes the passband asa function of excitation of an actuator.

Example 24 includes the system of any one of examples 18 to 23,including or excluding optional features. In this example, theadjustable pass filter is a micro-electro-mechanical (MEMS) Fabry-Perotinterferometer (FPI).

Example 25 includes the system of any one of examples 18 to 24,including or excluding optional features. In this example, theadjustable pass filter is a piezo-actuated Fabry-Perot interferometer(FPI).

Example 26 includes the system of any one of examples 18 to 25,including or excluding optional features. In this example, the globalreset is applied to the rolling shutter system after each facerecognition capture.

Example 27 is a tangible, non-transitory, computer-readable medium. Thecomputer-readable medium includes instructions that direct the processorto determine a passband that corresponds to a biometric captureapplication; adjust a voltage and frequency of an adjustable pass filterin response to the capture application and associated passband; and inresponse to a face recognition capture application, implement a globalshutter system and a rolling shutter sensor global reset.

Example 28 includes the computer-readable medium of example 27,including or excluding optional features. In this example, the biometriccapture application is one of a face recognition, iris scan, or eye gazeapplication.

Example 29 includes the computer-readable medium of any one of examples27 to 28, including or excluding optional features. In this example, asecond filter is to refine the passband via a plurality of stopbands.

Example 30 includes the computer-readable medium of any one of examples27 to 29, including or excluding optional features. In this example, theadjustable pass filter is a liquid crystal filter. Optionally, theliquid crystal filter comprises a plurality of liquid crystal layers,wherein each layer is to reflect or transmit particular passbands.

Example 31 includes the computer-readable medium of any one of examples27 to 30, including or excluding optional features. In this example, theadjustable pass filter is an electrochromatic filter.

Example 32 includes the computer-readable medium of any one of examples27 to 31, including or excluding optional features. In this example, theadjustable pass filter is a Fabry-Perot interferometer (FPI).Optionally, the Fabry-Perot interferometer (FPI) changes the passband asa function of excitation of an actuator.

Example 33 includes the computer-readable medium of any one of examples27 to 32, including or excluding optional features. In this example, theadjustable pass filter is a micro-electro-mechanical (MEMS) Fabry-Perotinterferometer (FPI).

Example 34 includes the computer-readable medium of any one of examples27 to 33, including or excluding optional features. In this example, theadjustable pass filter is a piezo-actuated Fabry-Perot interferometer(FPI).

Example 35 includes the computer-readable medium of any one of examples27 to 34, including or excluding optional features. In this example, theglobal reset is applied to the rolling shutter system after each facerecognition capture.

Example 36 is an apparatus for a combined camera system. The apparatusincludes instructions that direct the processor to a means to tune afilter, wherein a passband of the filter is electrically adjusted; and arolling shutter sensor, wherein an adjustable filter is to implement aglobal shutter and a rolling shutter sensor global reset.

Example 37 includes the apparatus of example 36, including or excludingoptional features. In this example, the means to tune the filter is atunable IR pass filter.

Example 38 includes the apparatus of any one of examples 36 to 37,including or excluding optional features. In this example, the means totune the filter is a liquid crystal filter. Optionally, the liquidcrystal filter comprises a plurality of liquid crystal layers, whereineach layer is to reflect or transmit certain passbands.

Example 39 includes the apparatus of any one of examples 36 to 38,including or excluding optional features. In this example, the means totune the filter is an electrochromatic filter.

Example 40 includes the apparatus of any one of examples 36 to 39,including or excluding optional features. In this example, the means totune the filter is a Fabry-Perot interferometer (FPI). Optionally, theFabry-Perot interferometer (FPI) changes the passband as a function ofexcitation of an actuator. Optionally, the Fabry-Perot interferometer(FPI) is a micro-electro-mechanical (MEMS) Fabry-Perot interferometer(FPI). Optionally, the Fabry-Perot interferometer (FPI) is apiezo-actuated Fabry-Perot interferometer (FPI).

Example 41 includes the apparatus of any one of examples 36 to 40,including or excluding optional features. In this example, the apparatusincludes an IR filter, wherein the IR filter is to provide a sharpcutoff band to refine the adjustable passband of the means to tune thefilter.

Example 42 includes the apparatus of any one of examples 36 to 41,including or excluding optional features. In this example, the means totune the filter is adjusted for a passband that corresponds to abiometric recognition application.

Example 43 includes the apparatus of any one of examples 36 to 42,including or excluding optional features. In this example, theadjustable IR pass filter is adjusted for a passband that corresponds toa face recognition, iris scan, or eye gaze application on the fly.

It is to be noted that, although some aspects have been described inreference to particular implementations, other implementations arepossible according to some aspects. Additionally, the arrangement and/ororder of circuit elements or other features illustrated in the drawingsand/or described herein need not be arranged in the particular wayillustrated and described. Many other arrangements are possibleaccording to some aspects.

In each system shown in a figure, the elements in some cases may eachhave a same reference number or a different reference number to suggestthat the elements represented could be different and/or similar.However, an element may be flexible enough to have differentimplementations and work with some or all of the systems shown ordescribed herein. The various elements shown in the figures may be thesame or different. Which one is referred to as a first element and whichis called a second element is arbitrary.

It is to be understood that specifics in the aforementioned examples maybe used anywhere in one or more aspects. For instance, all optionalfeatures of the computing device described above may also be implementedwith respect to either of the methods or the computer-readable mediumdescribed herein. Furthermore, although flow diagrams and/or statediagrams may have been used herein to describe aspects, the techniquesare not limited to those diagrams or to corresponding descriptionsherein. For example, flow need not move through each illustrated box orstate or in exactly the same order as illustrated and described herein.

The present techniques are not restricted to the particular detailslisted herein. Indeed, those skilled in the art having the benefit ofthis disclosure will appreciate that many other variations from theforegoing description and drawings may be made within the scope of thepresent techniques. Accordingly, it is the following claims includingany amendments thereto that define the scope of the present techniques.

What is claimed is:
 1. An electronic device comprising: an infraredlight source to emit infrared light; a rolling shutter sensor; at leastone processor to: cause the rolling shutter sensor to output a firstsignal corresponding to a first frame of image data during exposure tothe infrared light, reset the rows of the rolling shutter sensor at asame time, cause the rolling shutter sensor to output a second signalcorresponding to a second frame of image data without exposure to theinfrared light from the infrared light source, determine a differencebetween the first signal and the second signal to generate an ambientinfrared free frame, and recognize a face based on the ambient infraredfree frame; and an adjustable filter, the at least one processor tochange at least one of a voltage or a center frequency of the adjustablefilter to switch the electronic device from a first mode to recognize aface to a second mode to detect at least one of an iris or an eye gaze.2. The electronic device of claim 1, further including an optical deviceto focus light onto the rolling shutter sensor via the pass filter. 3.The electronic device of claim 2, wherein the at least one processor isto adjust a focal length of the optical device.
 4. The electronic deviceof claim 1, wherein the adjustable filter is an electrochromaticadjustable filter that is electrically adjustable to vary wavelengthsthat can pass through the adjustable filter.
 5. The electronic device ofclaim 1, wherein the adjustable filter includes an actuator and a pairof mirrors, the actuator to change a distance between the pair ofmirrors to control a spectrum of light passing to the rolling shuttersensor.
 6. An electronic device comprising: means for emitting infraredlight; means for capturing video; means for processing image data fromthe video, the processing means to: cause the video capturing means tocapture a first signal corresponding to a first frame of image dataduring exposure to the infrared light, reset the rows of the videocapturing means at a same time, cause the video capturing means capturea second signal corresponding to a second frame of image data withoutexposure to the infrared light from the infrared light source, determinea difference between the first signal and the second signal to obtain anambient infrared free frame, and recognize a face based on the ambientinfrared free frame; and means for filtering light, the processing meansto change at least one of a voltage or a center frequency of thefiltering means to switch the electronic device from a first mode torecognize a face to a second mode to detect at least one of an iris oran eye gaze.
 7. The electronic device of claim 6, further includingmeans for focusing light onto the video capturing means.
 8. Theelectronic device of claim 7, wherein the processing means is to adjusta focal length of the focusing means.
 9. The electronic device of claim6, wherein the filtering means is to vary wavelengths that can passthrough the adjustable filter.
 10. The electronic device of claim 6,wherein the filtering means includes means for controlling a spectrum oflight passing to the video capturing means.
 11. An electronic devicecomprising: an adjustable filter; an infrared light source; a rollingshutter sensor; and at least one processor to execute instructions to:detect selection of one of an iris scan mode or an eye gaze detectionmode; cause the rolling shutter sensor to output a first signalcorresponding to a first frame of video during exposure to infraredlight emitted by the infrared light source, detect an iris or an eyegaze based on the first signal, detect selection of a face recognitionmode, change at least one of a voltage or a center frequency of theadjustable filter based on a switch from the iris scan mode or eye gazedetection mode to the face recognition mode, cause the rolling shuttersensor to output a first signal corresponding to a second frame of videoduring exposure to infrared light emitted by the infrared light source,globally reset the rows of rolling shutter sensor, cause the rollingshutter sensor to output a third signal corresponding to a third frameof video without exposure to the infrared light from the infrared lightsource, determine a difference between the second signal and the thirdsignal to obtain an ambient infrared free frame, and recognize a facebased on the ambient infrared free frame.
 12. The electronic device ofclaim 11, further including a pass filter to filter a subset of signalstransmitted through the adjustable filter.
 13. The electronic device ofclaim 12, further including an optical device to focus light onto therolling shutter sensor via the pass filter.
 14. The electronic device ofclaim 13, wherein the at least one processor is to adjust a focal lengthof the optical device.
 15. The electronic device of claim 11, whereinthe adjustable filter is an electrochromatic adjustable filter that iselectrically adjustable to vary wavelengths that can pass through theadjustable filter.
 16. The electronic device of claim 11, wherein theadjustable filter includes an actuator and a pair of mirrors, theactuator to change a distance between the pair of mirrors to control aspectrum of light passing to the rolling shutter sensor.